diff -r f5c40ab9e233 README
--- a/README	Tue Aug 18 22:25:16 2015 -0700
+++ b/README	Sun Aug 30 11:18:14 2015 +0300
@@ -45,6 +45,34 @@
 (This will fail if you *also* built at the top-level directory.  You should do a
 "make clean" at the toplevel first.)
 
+If you need an optimized version of Python, you type "make profile-opt" in the 
+top level directory. This will rebuild the interpreter executable using Profile 
+Guided Optimization (PGO). For more details, see the section bellow.
+
+
+Profile Guided Optimization
+---------------------------
+
+PGO takes advantage of recent versions of compilers, both GCC and Clang. If ran, 
+the "profile-opt" rule will do several steps. 
+
+First, the entire Python directory is cleaned for temporary files that may 
+resulted in a previous compilation. 
+
+Then, an instrumented version of the interpreter is built, using suitable
+compiler flags for each flavor. Note that this is just an intermediary step 
+and the binary resulted after this step is not good for real life workloads, as
+it has profiling instructions embedded inside. 
+
+After this instrumented version of the interpreter is built, the Makefile will 
+automatically run a training workload. This is necessary in order to profile the
+interpreter execution. Note also that any errors displayed at this step will not
+adversely affect the results.
+
+Finally, the last step is to rebuild the interpreter, using the information 
+collected in the previous one. The end result will be a the Python binary that is
+optimized and suitable for distribution or production installation. 
+
 
 What's New
 ----------